CONSTRUCTION METHOD OF WELL SHAFT THROUGH UNSTABLE CLAY MINE ROCKS Russian patent published in 2013 - IPC E21B7/06 

FIELD: mining.

SUBSTANCE: when the well shaft is being constructed through unstable clay mine rocks, a vertical section is built. The section of initial deviation is drilled with increase in and stabilisation of a zenith angle of less than 60° by means of a navigation telemetric system. Flushing fluid is used with the base represented with clay flushing fluid with density ρ=1250-1400 kg/m³ with addition of modified disperse silica in the quantity of 0.1-0.3 vol. %. Casing string is lowered to the well with entry to upper lime, and casing string annulus is cemented. Productive part is opened by drilling the shaft using polymer-clay solution with density ρ=1112-1200 kg/m³ with increase in the zenith angle required for achieving the horizontal plane in the middle of the project formation.

EFFECT: avoiding cases of severe accidents when developing unstable rocks at high zenith angle.

1 dwg